Radio receiving system



June 6, 1939. J. F. DREYER, JR

RADIO RECEIVING SYSTEM Filed Nov. 27, 1937 R. .J R Y All En. m ma. T f J I.. .V w A NN J m. .n l W Alg# 5 Tm To; lo I T Q, C m W W @NJ .mw/w W n m.. m Saz .u m I n 52 IW .my I Q). Q H mf IIHMM Q C F .HN Ad Mv QF f| I l: `N.\\ `M,\ /q `w\ Patented June 6, 1939 t Si 2,161,616

UNITED STATES PATENT OFFICE RADIO RECEIVING SYSTEM John F. Dreyer, Jr., Brooklyn, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application November 27, 1937, Serial No. 176,779

Claims. (Cl. Z50-27) This invention relates in general to radio rein the copending application of W. J. OBrien, ceiving systems, and more particularly to a circuit Serial No. 759,327, led December 27, 1934, and organization utilizing a push-pull amplifier stage assigned to the same assignee as the present apfed directly from a preceding single tube stage plication. In that applicationit is explained that 5 which may function either as an amplifier or the tube exhibits negative transconductance from 5 as a detector of received signals. the signal control grid toward the grid (or auxil- It has been customary in prior practice to use iary anode) interposed between cathode and sigtransformer coupling between the output of a nal grid as well as a positive transconductance topreceding single tube amplier or detector stage ward the anode. As further explained in said colO and the input to a succeeding push-pull stage, pending application, the object of providing the because this form of coupling enables the applicanegative transconductance grid is to effect subtion of equal voltages to the control grids of the stantial compensation for the inherent capacity push-pull tubes but in phase opposition. It is existing in the input grid to cathode circuit also known, in order to avoid the use of transwhereby all frequencies Within a. comparatively former coupling, to utilize resistance-capacity wide range maybe amplified Vwith substantial coupling, and for obtaining the necessary phase uniformity. According tov the present invention opposition on the push-pull grids there is emhowever, advantage is taken of the fact that with ployed an auxiliary tube known as a phase rerespect to the control grid the tube has an auxilversing tube. A circuit embodying the last iary grid-like electrode or anode which exhibits a named suggestion is disclosed in the Gorton negative transconductance, which grid-like` elec- '20 United States Patent No. 1,654,075. trode together with the regular anode A are Y It is one of the main objects of the present inutilized as output electrodes. vention to provide an improved circuit arrange- It was found however, that theregular output ment wherein not only is the use of transformer anode of the tube operated with the characteriscoupling avoided, but the phase reversing tube of tic of a tetrode, i. e., high mu, high plate imped- .25

the Gorton patent is also dispensed with in the ance, whereas the auxiliary grid-like anode excoupling of a. single tube stage .to a push-pull hibited a rather low negative mu. In order that amplifier stage. the tube may be efficiently adapted for the pur- Another object of the invention is to provide a pose intended it is necessary that the transconsimpliiied circuit arrangement that will be efductances be substantially equal but opposite in 30 cient in operation and inexpensive to manufacsense,v In order that the auxiliary grid-like ture. anode may operate to produce a higher amplifica- Other objects and advantages of the invention tion factor and a higher impedance to substanwill become apparent to those skilled in the art tially simulate the characteristic of the regular as the description thereof proceeds. For a better anode, the additional screenS- is interposed be- S35 understanding of the invention however, refertween the control grid 3 and the grid 2. The ence is made to the following specification taken screen S has impressed on it a suitable positive in connection with the accompanying drawing potential and may conveniently bev connected to which illustrates a circuit embodying the inthe lead I5 which supplies potential to the screen vention. grid 5. 40

.Referring to the drawing, the circuit is shown An input circuit I0 `is connected between the to comprise a first tube D which is provided with signal control grid 3 and cathode C. The usual a cathode C, an anode A, and between said elecbiasing resistance II and by-pass condenser I2 trodes are interposed a plurality of grid electrodes, are connected in the lead to the cathode C for marked I, 2, 3, 4, and 5. Grid I serves as the impressing a suitable initial negative bias on `.45 space charge grid and substantially limits the the control grid. A load resistor I3 has one end total current emitted from the cathode and preconnected. to the anode A and its other end convents the Voltage variations of grid 2 from subnected to the double grid 2 4'. A source of voltstantially changing this current value, and by age supply I 4 such as a battery or the like, has

reason thereof the tube is inherently balanced in its negative terminal connected to the cathode .50 so far as cathode variations are concerned. Grids and its positive terminal connected through the 2 and 4 are tied together within the tube enlead I5 to the mid-point of the resistor I3. The velope and serve as auxiliary anodes; grid 3 is the screen grid 5 has impressed on it a potential signal control grid, and grid 5 acts as a screen lower than that impressed on anode A and grids grid. A tube such as thus far described is shown 2 4, by means of the lead I6 to an intermediate 55 point on the source I4 The space charge grid I is shown connected directly to cathode, but if desired this grid may be given a slightly negative or a slightly positive potential with respect to the cathode.

The push-pull tubes P and P' are of the pentode type, each containing a cathode C', signal control grid I', screen grid 2', suppressor grid 3', and anode A'. The signal grid I' of tube P is connected to the anode side of resistor I3 through the coupling condenser I'I, and the signal gridy I of tube P' is connected through a similar coupling condenser II to the double screen side of the resistor I3. A grid leak resistor I8 is connected between each signal grid I and ground, and resistor I9 and by-pass condenser 20 constitute the usual biasing network for the signal grids An output transformer 2| is connected in the anode or output circuits of the push-pull tubes P and P', and the connection 22 from the source I4 to the mid-tap of the transformer primary supplies D. C. operating potential to the anodes A' of the tubes. The same connection also furnishes suitable operating potential to the screen grids 2', 2 of the tubes.

The tube D may be caused to operate either as a detector or as an ampliiier. When operating as a detector the push-pull stage will be the power amplifier stage feeding into a utilization means such as the loudspeaker of the receiver. However, when operating as an ampliiier the detected signals from a preceding detector tube are fed to the input circuit I0, the tube D serving-as a iirst stage of audio, and the push-pull stage coupled thereto will then operate as the second or nal amplifier stage. In either case, there will appear at the terminals of the load resistor I3 potentials of equal value which will vary with the signal but in phase opposition. The potentials so developed across the resistor I3 are then fed to the signal grids through the respective capacity-resistance networks I'I-I8 to the grids I, I' of the push-pull tubes P and P' which operate in the conventional manner.

While the invention has been disclosed in a particular form it is to be understood that it is capable of embodiment in other forms without departing from the spirit and/or scope of the appended claims.

What I claim is:

1. In a receiving circuit, the combination of a vacuum tube having a cathode, a signal control grid, a plate and an additional grid interposed between cathode and the signal grid, suitable potentials impressed on said electrodes whereby said control grid exhibits a negative transconductance to said additional grid and a positive transconductance to said plate, an auxiliary grid interposed between the signal grid and the additional grid for substantially equalizing said transconductances, an impedance connected between the plate and the additional grid for utilizing the eiiect of the substantially equal and opposite transconductances, a pair of push-pull tubes, and a resistance-capacity combination coupling the opposite ends of said impedance to the input electrodes of said push-pull tubes.

. 2. A receiving circuit comprising a rst tube provided with a cathode, an anode and a plurality of interposed grid electrodes, a signal input circuit connected between one of said grids and the cathode, a load resistor connected between the anode and one of the other grid electrodes, a source of space current for said tube connected between cathode and the mid-point of said resistor, whereby said anode and grid to which the load resistor is connected have substantially equal potentials impressed thereon, another of said interposed grids which is adjacent to the control grid having impressed thereon a potential lower than that of the anode, a push-pull amplifier stage fed from said first tube, and means connecting the signal grids of the pushpull tubes to the opposite ends of said resistor.

3. A receiving circuit comprising a tube provided with a cathode, an anode and a plurality of interposed grid electrodes one of which is a signal control grid, means for biasing said control grid whereby the tube will operate as a biased detector, a signal input circuit connected between said control grid and cathode, a load resistor connected between the anode and one of the other grid electrodes, a source of space current for said detector tube connected between cathode and the mid-point of said resistor, whereby said anode and grid to which the load resistor is connected have substantially equal potentials impressed thereon, another of saidinterposed grids which is adjacent to the control grid having impressed thereon a potential lower than that of the anode, a push-pull amplier stage fed from said detector tube, and means including resistance and capacity connecting the grid to cathode circuits of. the push-pull tubes to the opposite ends of said resistor.

4. In a receiving circuit, the combination of a Vacuum tube having a cathode, a signal control grid, a plate and iirst, second and third grids interposed between cathode and signal grid, a connection from the first grid to the cathode whereby said grid is maintained at cathode potential, substantially equal positive potentials impressed on the second grid and on the plate, and a lower positive potential impressed on the third grid, an impedance connected between said second grid and plate, a pair of vacuum tubes connected in push-pull relation, and a resistancecapacity combination coupling the opposite ends of said impedance to the input electrodes of said push-pull tubes.

5. In a receiving circuit, the combination of a vacuum tube having a cathode, a grid-anode, a signal control grid and a plate-anode arranged in the order named, substantiallyequal positive potentials impressed on said grid-anode and.

rplate-anode whereby said control. grid exhibits a y negative transconductance to said grid-anode and a positive transconductance to said plate-anode, which transconductances are unequal, and means for substantially equalizing said transconductances comprising an auxiliary grid interposed between the signa-l grid and the grid-anode and having impressed thereon a positive potential lower than that of the anodes, an impedance ,connected between the anodes for utilizing the elTect of the substantially equal and opposite transconductances, a pair of push-pull tubes, and a resistance-capacity combination coupling the opposite ends of said impedance to the input electrodes of said push-pull tubes.

JOHN F. DREYER, JR. 

